This descriptive transversal epidemiological study had the objective of comparing the elderly population who took the influenza vaccine and who did not regarding the occurrence of events of diseases or hospital admittances within three months after the vaccination. It was not possible to work with probable sampling and the attempt of pairing the vaccinated and non-vaccinated elderly was not successful due to the high vaccine coverage observed (73% of the target population) and due to the short time available to make the interviews. The result of the descriptive analysis of the 1,130 elderly interviewed was quite interesting even not being possible to infer it regarding the universe of the elderly population from Porto Alegre. We found a higher proportion of vaccinated people in the age group of 70 to 79 years old (42%), and a prevalence of non-vaccinated among the age group of 60 to 64 years old (40%). The vaccinated elderly were mostly older; female, who have private health care insurance; with higher income; that perform physical activities and non-smokers. The non-vaccinated were mostly men; younger; with lower income; that do not perform physical exercises; and smoke. A lower percentage of pneumonias reports and hospital admittances was observed among the vaccinated in comparison to the non-vaccinated people.